Nonintrusive inspection system

ABSTRACT

An x-ray technique-based nonintrusive inspection apparatus is provided which is capable of inspecting 600 containers an hour which is small, and which is easily maintainable. Features of the apparatus include “radiation locking” with “active curtains”, “continuous scanning” utilizing an x-ray line scanner subsystem and a CT scanner subsystem, good structural integrity, radiation containment in a self-shielding manner, an easily maintainable driving arrangement, shielding curtains that can be raised and lowered quickly, a container jam release mechanism, and efficient air conditioning.

CROSS-REFERENCE TO OTHER APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 10/071,993,filed on Feb. 7, 2002, which is a divisional of U.S. patent applicationSer. No. 09/794,505 (issued as U.S. Pat. No. 6,430,255), filed on Feb.26, 2001, which is a continuation of prior Application No.PCT/US99/28229, filed on Nov. 29, 1999, which claims priority from U.S.Provisional Patent Application No. 60/110,417, filed on Nov. 30, 1998.

BACKGROUND TO THE INVENTION

1.) Field of the Invention

This invention relates to an x-ray technique-based nonintrusiveinspection apparatus. An x-ray technique-based nonintrusive inspectionapparatus according to the invention may, for example, be used fornonintrusively inspecting closed containers before being loaded into aloading bay of an aircraft, or may include technologies which may findapplication in other similar or different inspection apparatus.

2.) Discussion of Related Art

Inspection apparatus are commonly used for nonintrusively inspectingluggage and other closed containers before being loaded into a loadingbay of an aircraft. Older generation inspection apparatus relied merelyon conventional x-ray technology for nonintrusively inspecting closedcontainers. More recently, inspection apparatus which rely on computertomography (CT) scanning technology have also been utilized. Aninspection apparatus utilizing CT scanning technology is described inU.S. Pat. Nos. 5,182,764 and 5,367,552 by Peschmann et al. which areassigned to the assignee of the present case and which are herebyincorporated by reference.

SUMMARY OF THE INVENTION

The invention provides an x-ray technique-based nonintrusive inspectionapparatus which allows for “radiation locking” as will be described inmore detail in the description that follows. The inspection apparatusincludes loading inspection and unloading tunnel sections, first, secondand third conveyor apparatus, an x-ray source, first, second, third andfourth actuation devices, and first, second, third and fourth radiationresistant closure members.

Each tunnel section has a respective first end and a respective secondend opposing the first end thereof. The inspection tunnel section islocated in line after the loading tunnel section so that the second endof the loading tunnel section is adjacent the first end of theinspection tunnel section. The unloading tunnel section is located inline after the inspection tunnel section so that the second end of theinspection tunnel section is located adjacent the first end of theunloading tunnel section.

The first conveyor apparatus has at least one conveyor belt which is atleast partially located within the loading tunnel section and which,upon movement, is capable of moving an object from the first end of theloading tunnel section to the second end of the loading tunnel section.The second conveyor apparatus has at least one conveyor belt which is atleast partially located within the inspection tunnel section and which,upon movement, is capable of moving an object from the first end of theinspection tunnel section to the second end of the inspection tunnelsection. The third conveyor apparatus has at least one conveyor beltwhich is at least partially located within the unloading tunnel sectionand which, upon movement, is capable of moving an object from the firstend of the unloading tunnel section to the second end of the unloadingtunnel section.

The x-ray source, when operated, creates radiation within the inspectiontunnel section.

The first closure member is movable by the first actuation devicebetween an open position wherein the first end of the loading tunnelsection is open, and a closed position wherein the first closure membercloses the first end of the loading tunnel section. The second closuremember is movable by the second actuation device between an openposition wherein the second end of the loading tunnel section is incommunication with the first end of the inspection tunnel section toallow for movement of an object from the loading tunnel section to theinspection tunnel section, and a closed position wherein the secondclosure member substantially closes off communication between the firstand inspection tunnel sections. The third closure member is movable bythe third actuation device between an open position wherein the secondend of the inspection tunnel section is in communication with the firstend of the unloading tunnel section to allow for movement of an objectfrom the inspection tunnel section to the unloading tunnel section, anda closed position wherein the third closure member substantially closesoff communication between the second and unloading tunnel sections. Thefourth closure member is movable by the fourth actuation device betweenan open position wherein the second end of the loading tunnel section isopen, and a closed position wherein the fourth closure member closes thesecond end of the unloading tunnel section.

The inspection apparatus may further include first, second, third andfourth curtain rollers, each being rotatable by a respective one of theactuation devices. The closure members may be curtains and each curtainmay be secured to a respective curtain roller so as to be rolled onto orfrom the curtain roller upon rotation of the curtain roller.

The inspection apparatus may further include a controller which controlspower supplied to the respective actuation devices. The controller maybe programmed to synchronize the actuation devices so that, at leastwhen the x-ray source creates radiation within the inspection tunnelsection, at least one of the first and second closure members is in itsrespective closed position and at least one of the third and fourthclosure members is in its respective closed position. The controller mayturn the radiation source off when both the first and second closuremembers are not entirely in their respective closed positions, or whenboth the third and fourth closure members are not entirely in theirrespective closed positions.

The invention also provides a method of nonintrusively inspecting anobject in a “radiation locking” manner, utilizing an x-raytechnique-based nonintrusive inspection apparatus, that permits x-raysgenerated in an inspection tunnel section thereof to remain oncontinuously. A first radiation resistant closure member is moved intoan open position wherein a first end of a loading tunnel section isopen, while a second radiation resistant closure member is in a closedposition wherein it closes a second end of the loading tunnel sectionopposing the first end of the loading tunnel section. An object is movedthrough the first end of the loading tunnel section into the loadingtunnel section while the second closure member remains in its closedposition. The first closure member is then moved into a closed positionwherein the first closure member closes the first end of the firsttunnel. After movement of the first closure member into its closedposition, the second closure member is moved into an open positionwherein the second end of the loading tunnel section is in communicationwith a first end of a inspection tunnel section. The object is thenmoved from the loading tunnel section into the inspection tunnelsection. After movement of the object into the inspection tunnelsection, the second closure member is moved into its closed position soas to substantially close off communication between the first andinspection tunnel sections. The object is then radiated within theinspection tunnel section.

The confines of the inspection tunnel section may be radiated while theobject is moved into the loading tunnel section.

The first closure member may remain in its closed position while theobject is moved into the inspection tunnel section. The confines of theinspection tunnel section may be radiated while the object is moved intothe inspection tunnel section.

The invention also provides a method of nonintrusively inspecting anobject by simultaneously utilizing an x-ray line scanner subsystem and aCT scanner subsystem, in an x-ray technique-based nonintrusiveinspection apparatus, which may be in a close relationship relative toone another. A front portion of the object is first scanned utilizingthe x-ray line scanner subsystem. A section within the front portion ofthe object is scanned utilizing a CT scanner subsystem. A rear portionof the object is then scanned, utilizing the x-ray line scannersubsystem, after the section in the front portion is scanned utilizingthe CT scanner subsystem.

The object may, for example, be a closed container which isnonintrusively inspected.

The object may be scanned while being moved relative to the x-ray linescanner subsystem and the CT scanner subsystem, and the front portionand the rear portion may be scanned without altering the direction ofmovement of the object relative to the x-ray line scanner subsystem andthe CT scanner subsystem, although it may be necessary to bring theobject to a halt relative to the CT scanner subsystem. Movement of theobject relative to the x-ray line scanner subsystem and the CT scannersubsystem may be progressively reduced after the section is scanned bythe x-ray line scanner subsystem but before the section is scanned bythe CT scanner subsystem.

The invention also provides an x-ray technique-based nonintrusiveinspection apparatus having both x-ray and CT scanning capabilitieswithin a single tunnel section. The inspection apparatus includes atleast one tunnel section, a conveyor apparatus, an x-ray line scannersubsystem, and a CT scanner subsystem. The tunnel section has first andsecond opposed ends. The conveyor apparatus has at least one conveyorbelt which is at least partially located within the tunnel section. Theconveyor belt, upon movement, is capable of transporting an object fromthe first end to the second end of the tunnel section. The x-ray linescanner subsystem is positioned to scan at a first plane within thetunnel section. The CT scanner subsystem is positioned to scan at asecond plane within the tunnel section.

The first and second planes may be located by distance of less than 110centimeters from one another.

Preferably, the same conveyor belt conveys the object from the firstplane to the second plane.

The inspection apparatus may further include a base frame, and a supportstructure having a lower end secured to the base frame and extendingupwardly therefrom, and the x-ray line scanner subsystem and the CTscanner subsystem may both the mounted to the support structure.

The invention also provides an x-ray technique-based nonintrusiveinspection apparatus having good structural integrity. The inspectionapparatus includes a base frame of monocoque design, a supportstructure, and a CT scanner subsystem. The support structure is securedto the base frame. The CT scanner subsystem is rotatably mounted to thesupport structure. Although having specific application for x-raytechnique-based nonintrusive inspection apparatus used for detectingcontraband in closed containers, inspection apparatus are alsoenvisioned having base frames of monocoque design which are notnecessarily used for the detection of contraband within closedcontainers.

A motor may be coupled to the CT scanner subsystem so as to rotate theCT scanner subsystem, for example at a rate of at least 100 revolutionsper minute.

The CT scanner subsystem may define an opening having a cross-dimensionof at least 110 centimeters.

The CT scanner subsystem may define an opening and the inspectionapparatus may further include a conveyor apparatus mounted to the baseframe. The conveyor apparatus may have a conveyor belt which passesthrough the opening. The conveyor belt may have a width of at least 90cm.

The CT scanner subsystem may include a gantry enclosure, a radiationsource mounted on one side to the gantry enclosure so that, when theradiation source is operated, the confines of the gantry enclosure areradiated, the gantry enclosure being at least partially made of lead.

The invention also provides a CT scanner subsystem of a nonintrusiveinspection system which is at least partially self shielded so as toattenuate leaking of radiation therefrom to acceptable levels. The CTscanner subsystem may include first and second spaced gantry plates, atleast one spacer, a ring, and an x-ray source. The first and secondgantry plates each have a respective gantry aperture formed therein. Theat least one spacer is located between the gantry plates so that the atleast one spacer together with the gantry plates define a partial gantryenclosure. The ring is located on the gantry enclosure and allows thegantry enclosure to be mounted to a support structure for rotation aboutan axis through the gantry apertures. The x-ray source is secured to thegantry enclosure at one side thereof so that, when the x-ray source isoperated, the confines of the gantry enclosure are at least partiallyradiated. The gantry enclosure is at least partially made of a materialwhich substantially attenuates radiation leakage from the gantryenclosure i.e. by a degree which is much more than for exampleattenuation of radiation with steel. The gantry enclosure may forexample include a liner of lead or another material which, substantiallyattenuates radiation leakage on the first or second gantry plates or onthe spacer. The x-ray source may include an x-ray tube and a liner, oflead or another material which substantially attenuates radiationleakage, on the x-ray tube.

The invention also provides an x-ray technique-based noninstrusiveinspection apparatus including a support frame, a CT scanner subsystem,and a tunnel portion. The CT scanner subsystem may include first andsecond spaced gantry plates, at least one spacer, and an x-ray source.Each gantry plate may have a respective gantry aperture formed therein.The at least one spacer may be located between the gantry plates so thatthe at least one spacer together with the gantry plates define a partialgantry enclosure. The x-ray source may be secured to the gantryenclosure at one side thereof so that, when the x-ray source isoperated, the confines of the gantry enclosure are at least partiallyradiated. The gantry enclosure is at least partially made of a materialwhich substantially attenuates radiation leakage from the gantryenclosure. The CT scanner subsystem is mounted to the support frame forrotation about an axis through the first and second gantry apertures.The tunnel portion is nonrotatably mounted to the support frame and hasan end which mates with the gantry aperture in the first gantry plate.The tunnel portion is also at least partially made of a material whichsubstantially attenuates radiation leakage from the tunnel portion.

The invention also provides an x-ray technique-based noninstrusiveinspection apparatus which is easily maintainable because of thelocation of a flexible member such as a belt or a chain which is usedfor driving a CT scanner subsystem of the inspection apparatus. Theinspection apparatus includes a support frame, a CT scanner subsystem,at least first, second and third pulleys, and a flexible member. The CTscanner subsystem is rotatably mounted to the support frame and has acircular outer surface. The first, second and third pulleys are mountedaround the CT scanner subsystem to the support frame. The flexiblemember runs over the first, second and third pulleys. A first section ofthe flexible member runs from the first pulley to the second pulley in afirst direction around and over the circular outer surface. A secondsection of the flexible member returns from the second pulley over thethird pulley back to the first pulley in a second direction, opposite tothe first direction, around the circular outer surface.

According to one aspect of the invention, an x-ray technique-basednonintrusive inspection apparatus is provided including at least a firsttunnel section, an x-ray source, at least a first actuation device, andat least a first radiation resistant closure member. The first tunnelsection has first and second opposed ends. The x-ray source, whenoperated, creates radiation within the first tunnel section. The firstradiation resistant closure member is movable by the actuation devicebetween an open position wherein the first end of the first tunnelsection is open, and a closed position wherein the first closure membercloses the first end of the first tunnel section. The inspectionapparatus thus has an “active” closure member. Specific advantages ofactive closure members are discussed in the description that follows.

The inspection apparatus may include a tensioning roller which isrotatably mounted to the support frame. The tensioning roller acts onthe curtain and tends to roll the curtain from the curtain roller.

The inspection apparatus may further include a spring which is biasedbetween the support frame and the tensioning roller so as to tend torotate the tensioning roller.

The inspection apparatus may further include a sheet which has a firstportion attached to the curtain roller and a second portion attached tothe tensioning roller, so as to connect the tensioning roller to thecurtain. The sheet may be secured to the curtain roller withoutintervention by the curtain.

The curtain preferably hangs from one side of the curtain roller and thetensioning roller is preferably located on the same side of the curtainroller as the side of the curtain roller from which the curtain hangs.

The invention also provides an effective manner of making a collimatorfor a detector array of the x-ray detection apparatus. First, a die isinjected with a material. The material is then allowed to set within thedie to form a body. The body is then removed from the die. The bodytypically includes a support structure and a plurality of septa securedto the support structure.

The material preferably includes a first, lead component comprising atleast 90 percent thereof. The material may include a second componentwhich is stronger than lead. The second component may, for example,include tin.

According to the method, a collimator for a detector array may be formedwherein septa of the collimator converge. The collimator may include abody which includes a support structure and a plurality of septa securedto the support structure. Center lines of two of the septa located nextto one another converge in a first direction so that the septa may bealigned with a radiation source, but surfaces of the two septa facingone another do not converge in the first direction so as to allow forremoval of the body from a die which is used to form the body.

The invention also provides a collimator for a detector array of anx-ray inspection apparatus, which includes a body which includes atleast one support structure and a plurality of septa secured to thesupport structure. The body is made of a material having a first, leadcomponent comprising at least 90 percent thereof.

For added strength, the body may include first and second supportstructures with the septa secured between the first and second supportstructures.

The invention also provides a collimator for a detector array of anx-ray inspection apparatus which allows for modular design of detectorarrays. The collimator includes a body having a plurality ofregistration formations thereon. The body includes a support structureand a plurality of septa secured to the support structure.

Each registration formation may be a respective notch in a portion ofthe body.

The invention also provides an x-ray technique-based nonintrusiveinspection apparatus which allows for easy release of parts ofcontainers which become jammed between rollers of conveyor apparatuswhich are located sequentially one after the other. The inspectionapparatus includes a base frame, a tunnel section, a conveyor beltmounting structure, front and rear conveyor rollers, and a conveyorbelt. The tunnel section has a first end and a second end opposing thefirst end, and is mounted to the base frame. The front and rear rollersare rotatably mounted to the conveyor belt mounting structure. Theconveyor belt runs over the front and rear conveyor rollers. Theconveyor belt mounting structure is mounted to the base frame for atleast limited movement, between first and second positions, in adirection in which the conveyor belt moves between the front and rearconveyor rollers. The conveyor belt extends at least some distancebetween the first and second ends through the tunnel section.

The invention also extends to a method of assembling an x-raytechnique-based nonintrusive inspection apparatus wherein a conveyorbelt of the inspection apparatus is preinstalled and wherein theconveyor belt may be pre-tensioned. A conveyor belt mounting structure,having front and rear conveyor rollers rotatably mounted thereto, and aconveyor belt over the front and rear conveyor rollers, is mounted to abase frame. The conveyor belt mounting structure is mounted to the baseframe for at least limited movement between first and second positionsin a direction in which the conveyor belt moves over the front and rearconveyor rollers.

The invention also provides an x-ray technique-based nonintrusiveinspection apparatus having a housing which is designed, for purposes ofkeeping contaminants from entering the housing, to have a higherpressure inside the housing than externally of the housing. Thenonintrusive inspection apparatus includes a base frame, tunneling, anx-ray source, paneling, and a fan. The tunneling is mounted to the baseframe and has a first end and a second end opposing the first end. Thex-ray source which, when operated, creates radiation within thetunneling. The paneling is located around the tunneling and the x-raysource so that the paneling and the base frame jointly define a housingaround the tunneling and the x-ray source. The housing has an entryaperture in proximity to the first end, and an exit aperture inproximity to the second end of the tunneling. The housing also has anair inlet opening. The fan is positioned to draw air through the inletopening into the housing. The housing is formed, the entry apertureseals with the first end of the tunneling to an extent sufficient, andthe exit aperture seals with the second end of the tunneling to anextent sufficient so that the confines of the housing are at a higherpressure than externally of the housing when the fan draws into thehousing.

The invention also provides an x-ray technique-based nonintrusiveinspection apparatus which may be cooled without necessarily having afan mounted to a rotating gantry enclosure thereof. The nonintrusiveinspection apparatus includes a support frame, a CT scanner subsystem, aplenum, an air-conditioning unit, and a duct. The CT scanner subsystemis rotatably mounted to the support frame and has a gantry enclosure. Atleast one air passage is formed into the gantry enclosure. The plenum isnonrotatably mounted to the support frame. The plenum is locatedexternally of the gantry enclosure over the air passage so that theconfines of the plenum are in communication with the air passage. Theair-conditioning unit includes a fan. The duct connects theair-conditioning unit with the plenum. When the fan is operated, airpasses from the air-conditioning unit through the duct to the plenum,from the plenum through the air passage into the gantry enclosure, andfrom the gantry enclosure through the radiator.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of example with reference tothe accompanying drawings wherein like reference numerals indicate likeor similar components and wherein:

FIG. 1 is a perspective view of an x-ray technique-based nonintrusiveinspection apparatus according to an embodiment of the invention;

FIG. 2 is a cross-sectional side view representing some of thecomponents of the inspection apparatus of FIG. 1;

FIG. 3 a is a side view representing the inspection apparatus of FIG. 2before a first container and a second container are moved into a loadingtunnel section of the inspection apparatus;

FIG. 3 b is a view similar to FIG. 3 a after the first container ismoved into the loading tunnel section;

FIG. 3 c is a view similar to FIG. 3 b after a first radiation resistantcurtain is closed behind the first container;

FIG. 3 d is a view similar to FIG. 3 c after a second radiationresistant curtain in front of the first container is opened;

FIG. 3 e is a view similar to FIG. 3 d while the first-container ismoved into and inspection tunnel section of the inspection apparatus;

FIG. 3 f is a view similar to FIG. 3 e after the first container islocated entirely within the inspection tunnel section and the secondradiation resistant curtain is closed behind the first container;

FIG. 3 g is a view similar to FIG. 3 f after a third radiation resistantcurtain in front of the first container is opened and while the firstcontainer is moved into an unloading tunnel section of the inspectionapparatus, and after the second container is moved into the loadingtunnel section;

FIG. 3 h is a view similar to FIG. 3 g after the first container islocated entirely within the unloading tunnel section and the thirdradiation resistant curtain is closed behind the first container, andafter the first radiation resistant curtain is closed behind the secondcontainer;

FIG. 3 i is a view similar to FIG. 3 h after a fourth radiationresistant curtain in front of the first container is opened and thefirst container is moved out of the unloading tunnel section, and afterthe second radiation resistant curtain is opened in front of the secondcontainer;

FIG. 3 j is a view similar to FIG. 3 i after the fourth radiationresistant curtain is closed behind the first container, after the secondcontainer is moved into the inspection tunnel section, and after thesecond radiation resistant curtain is closed behind the secondcontainer;

FIG. 4 a(i) is a view similar to FIG. 3 e, further illustrating thepositioning of the container relative to an imaging plane of an x-rayline scanner subsystem forming part of the inspection apparatus;

FIG. 4 a(ii) is a plan view of the container in FIG. 4 a(i);

FIG. 4 b(i) is a view similar to FIG. 3 f, further illustrating thepositioning of the container relative to the imaging plane of the x-rayline scanner subsystem and an imaging plane of a CT scanner subsystemforming part of the inspection apparatus when the CT scanner subsystemis used for scanning at a location of interest within the container thatmay correspond with an object of interest;

FIG. 4 b(ii) is a plan view of the container in FIG. 4 b(i);

FIG. 4 c(i) is a view similar to FIG. 3 g, further illustrating thepositioning of the container relative to the respective imaging planesof the x-ray line scanner subsystem and the CT scanner subsystem whenthe CT scanner subsystem is used for scanning another location ofinterest within the container;

FIG. 4 c(ii) is a plan view of the container in FIG. 4 c(i);

FIG. 5 is a perspective view of a support frame forming part of theinspection apparatus and the CT scanner subsystem;

FIG. 6 is a cross-sectional side view which illustrates how radiation isshielded within the inspection tunnel section;

FIG. 7 is a perspective view illustrating in exploded form a gantryenclosure forming part of the CT scanner subsystem;

FIG. 8 is an end view illustrating a driving arrangement which is usedfor rotating the CT scanner subsystem;

FIG. 9 is a perspective view of a shielding arrangement which isincorporated into a shielding apparatus forming part of the x-raytechnique-based nonintrusive inspection apparatus;

FIG. 10 is an end view of the shielding arrangement of FIG. 9 before aradiation resistant curtain thereof is rolled onto a curtain rollerthereof;

FIG. 11 is a view similar to FIG. 10 while the curtain is rolled ontothe curtain roller, further illustrating the effect of a tensioningapparatus which controls rolling of the curtain onto the curtain roller;

FIG. 12 a(i) is a cross-sectional side view of a die which is used toform a detector array collimator of the inspection apparatus,illustrating the die in exploded form;

FIG. 12 a(ii) is a cross-sectional end view of the die of FIG. 12 a(i);

FIG. 12 b(i) is a view similar to FIG. 12 a(i) after the die isassembled and before a material is injected into the die;

FIG. 12 b(ii) is a cross-sectional end view of the die in FIG. 12 b(i);

FIG. 12 c(i) is a cross-sectional view of a detector array collimatorwhich is formed by injecting a material into the die of FIG. 12 b(i);

FIG. 12 c(ii) is a cross-sectional end view of the detector arraycollimator of FIG. 12 c(i);

FIG. 13 is a perspective view of the detector array collimator of FIG.11 c(i) and FIG. 11 c(ii);

FIG. 14 is a cross sectional view through septa of the detector arraycollimator of FIG. 13, illustrating in an exaggerated manner how thesepta are formed;

FIG. 15 is a perspective view of a portion of the inspection apparatus,illustrating how a conveyor system of the inspection apparatus ismounted to a base frame of the inspection apparatus;

FIG. 16 is a side view of the inspection apparatus, further illustratingpaneling which partially form a housing of the inspection apparatus; and

FIG. 17 is a side view of the inspection apparatus illustratingdiagrammatically how the inspection apparatus is air-conditioned;

DESCRIPTION OF THE INVENTION

Introductory Description

FIG. 1 and FIG. 2 of the accompanying drawings illustrate an x-raytechnique-based nonintrusive inspection apparatus 8 according to anembodiment of the invention. The inspection apparatus 8 includes asupport frame 10, a loading tunnel section 12, an inspection tunnelsection 14, an unloading tunnel section 16, a loading conveyor apparatus18, and inspection conveyor apparatus 20, an unloading conveyorapparatus 22, first, second, third and fourth shielding arrangements,24, 26, 28 and 30 respectively, a stationary x-ray line scannersubsystem 32, a rotating CT scanner subsystem 34, and a controller 36.

The support frame 10 includes a base frame 38 and an arch 40 whicharches in a plane perpendicular to the drawing and which is secured tothe base frame 38 on opposing sides of the arch 40. The x-ray linescanner subsystem 32 is mounted on one side of the arch 40 and the CTscanner subsystem 34 is mounted to the arch 40 for rotation in a planeperpendicular to the drawing on a side of the arch 40 opposing the x-rayline scanner subsystem 32.

Referring now in particular to FIG. 2, each tunnel section 12, 14 or 16has a respective first end 42 and a respective second end 44 opposingthe first end thereof. The inspection tunnel section 14 is located inline after the loading tunnel section 12 so that the second end 44 ofthe loading tunnel section 12 is adjacent the first end 42 of theinspection tunnel section 14. The unloading tunnel section 16 is locatedin line after the inspection tunnel section 14 so that the second end 44of the inspection tunnel section 14 is located adjacent the first end 42of the unloading tunnel section 16. All the tunnel sections 12, 14 and16 are mounted to the base frame 38.

Each conveyor apparatus 18, 20 or 22 is located within a respectivetunnel section 12, 14 or 16. Each conveyor apparatus 18, 20 or 22includes a respective front conveyor roller 46 near a respective firstend 42 of a respective tunnel section 12, 14 or 16, a respective rearconveyor roller 48 near a respective second end 44 of a respectivetunnel section 12, 14 or 16, and a conveyor belt 50 which runs over theconveyor rollers 46 and 48 and a supporting bed (not shown). Althoughnot shown in FIG. 2 so as not to obscure the drawing, it should beunderstood that each conveyor roller 46 and 48 of each conveyorapparatus 18, 20 and 22 is rotatably mounted to a respective bracketassembly and that each bracket assembly is secured to the base frame 38.It should also be understood that one of the conveyor rollers 46 or 48of each conveyor apparatus 18, 20 and 22 is rotated by a respectivemotor which is mounted to the base frame 38 but which is not shown inFIG. 2 so as not to obscure the drawing.

Each shielding arrangement 24, 26, 28 and 30 includes a respectivecurtain roller 54 and a respective radiation resistant curtain 56secured to the curtain roller 54. Although not shown in FIG. 2 so as notto obscure the drawing, it should be understood that each curtain roller54 is rotatably mounted to a respective support structure and that eachsupport structure is secured to the base frame 38. It should also beunderstood that each curtain roller 54 is rotated by a respective motorwhich may also be mounted to the support structure but which is notshown in FIG. 2 so as not to obscure the drawing. The curtain rollers 54are positioned so that each curtain 56 is located near an end 42 or 44of one or more of the tunnel sections 12, 14 and 16.

Rotation of the curtain roller 54 in one direction causes the curtain 56to be rolled from the curtain roller 54 which causes the curtain 56 todrop, and rotation of the curtain roller 54 in an opposite directionraises the curtain 56 by rolling the curtain 56 onto the curtain roller54.

When the curtain 56 is raised, the curtain 56 is moved into an “openposition” wherein the end or ends 42 or 44 are open, and when thecurtain is dropped the curtain is moved into a “closed position” whereinthe curtain 56 closes the end or ends 42 or 44.

For example, when the curtain 56 of the first shielding arrangement 24is moved into its open position, the first end 42 of the loading tunnelsection 12 is open, and when the curtain 56 of the first shieldingarrangement 24 is moved into its closed position, the first end 42 ofthe loading tunnel section 12 is closed.

Similarly, when the curtain 56 of the second shielding arrangement 26 ismoved into its open position, the second end 44 of the loading tunnelsection 12 is in communication with the first end 42 of the inspectiontunnel section 14, and when the curtain 56 of the second shieldingarrangement 26 is moved into its open position, communication betweenthe loading and inspection tunnel sections 12 and 14 is substantiallyclosed off.

Similarly, when the curtain 56 of the third shielding arrangement 28 ismoved into its open position, the second end 44 of the inspection tunnelsection 14 is in communication with the first end 42 of the unloadingtunnel section 16, and when the curtain 56 of the third screeningarrangement 28 is moved into its closed position, communication betweenthe inspection and unloading tunnel sections 14 and 16 is substantiallyclosed off.

Similarly, when the curtain 56 of the fourth shielding arrangement 30 ismoved into its open position, the second end 44 of the unloading tunnelsection 16 is open, and when the curtain 56 of the fourth shieldingarrangement 30 is moved into its closed position, the second end 44 ofthe unloading tunnel section 16 is closed.

Detectors (not shown) are positioned to detect the positioning of eachcurtain 56 independently. More detectors (not shown) are positioned todetect the positioning, speed and acceleration of each conveyor belt 50independently. More detectors (not shown) are positioned to detect thepositioning of containers at various locations within the inspectionapparatus 8.

The controller 36 is in communication with the detectors. A disk orother computer readable medium may be provided on which an executableprogram is stored. The controller 36 may, for example, be a computerwhich is capable of reading the program on the disk and may includememory in the program is stored. The program, once executed mayautomatically synchronize movement of the curtains 56 and the conveyorbelts 50 in a manner which is generally referred to as “radiationlocking”. Radiation locking is further described hereinbelow withreference to FIG. 3 a to FIG. 3 j. The controller 36 also controls otheraspects of movement of containers through the inspection apparatus 8which are further described hereinbelow with reference to FIG. 4 a(i) toFIG. 4 c(ii). It can generally be noted that this stage that radiationlocking provides adequate shielding of x-ray radiation from people thatmay be located in an area around the inspection apparatus 8. Thecontroller 36 controls power supplied to the motors which drive theconveyor apparatus 18, 20 and 22 so as to control the positioning, speedand acceleration of the conveyor belts 50 of the conveyor apparatus 18,20 and 22. The controller 36 also controls power supplied to the motorswhich drive the curtain rollers 54 of the first, second and thirdshielding arrangement 24, 26, 28 and 30 so as to control thepositioning, speed and acceleration of the curtain rollers 54 of thefirst, second and third shielding arrangement 24, 26, 28 and 30.

One advantage of the inspection apparatus 8 illustrated in FIG. 2 isthat, because of adequate shielding due to radiation locking, there isno need for locating the conveyor apparatus 18, 20 and 22 so that theydefine an elaborate undulating path—the conveyor belts 50 are alllinearly aligned with one another, and are located within the samehorizontal plane (if, of course, the inspection apparatus 8 is locatedon a horizontal floor). When a technician has to enter any one of thetunnel sections 12, 14 or 16, the technician may easily enter the tunnelsection without the need for the technician to climb up an inclinedconveyor apparatus, as is often the case in certain prior art apparatus.

A further advantage of the fact that the conveyor belts 50 are alllinearly aligned is that the height of the overall apparatus can beminimized. In one example the inspection apparatus 8, ones enclosed by ahousing, has an overall height of about 223 centimeters. A furtheradvantage is that the maximum speed of objects passing through theinspection apparatus 8 is not constrained by the existence ofdiscontinuities in the belt path.

A further advantage of the inspection apparatus 8 is that the curtains56 are “active curtains” in the sense that each curtain 56 opens toallow for a container to pass 56 without obstruction by the curtain 56.The curtain 56 does therefore not create a volume of “dead space” bylying on top of the container. Larger objects can therefore be movedinto a respective tunnel section 12, 14 or 16 although each conveyorapparatus 18, 20 or 22 may have a smaller footprint. Larger containersare typically about 110 centimeters in length and in one example theloading tunnel section 12 has a length of about 135 centimeters and theunloading tunnel 16 has a length of about 135 centimeters. Because deadspace is minimized, the overall length of the apparatus is thusdecreased. Active curtains also have the advantage that they may allowfor passing through of heavier containers, which may for example be asmuch as one meter in height, but that very light weight containers mayalso pass through without being obstructed, there being no absoluteminimum weight requirement for passing through the active curtains.Larger light objects in particular may pass through easier than throughprior art passive curtains.

It should also be noted that the x-ray line scanner subsystem 32 and theCT scanner subsystem 34 operate within the same tunnel section, namelythe inspection tunnel section 14, without an intermediate radiationresistant curtain or other shielding device. By locating the x-ray linescanner subsystem 32 and the CT. scanner subsystem 34 within the sametunnel section, the overall length of the inspection apparatus 8 isreduced. As will be described in more detail hereinbelow, collimatorsprevent, or limit, interference between x-rays of the x-ray line scannersubsystem 32 and the CT. scanner subsystem 34.

Furthermore, it should be noted that the x-ray line scanner subsystem 32and the CT scanner subsystem 34 are both mounted to the same upwardlyextending support structure, namely the arch 40. By mounting the x-rayline scanner subsystem 32 and the CT scanner subsystem 34 both to thesame support structure, the orientation of the x-ray line scannersubsystem 32 and the CT scanner subsystem 34 relative to one another canbe more accurately controlled. In particular, the x-ray line scannersubsystem 32 may scan in a first plane and the CT scanner subsystem 34may scan in a second plane which is parallel to the first plane to amuch tighter tolerance. Parallelism between the first and second planesis important because it greatly reduces the complexity of software usedfor coordinating images received from the x-ray line scanner subsystem32 and the CT scanner subsystem 34.

It should also be noted that the same conveyor belt, namely the conveyorbelt 50 of the inspection conveyor apparatus 20, transports containerswhile being scanned respectively by the x-ray line scanner subsystem 32and the CT scanner subsystem 34. There is thus no transition from oneconveyor belt to another between the x-ray line scanner subsystem 32 andthe CT scanner subsystem 34. Because of the use of a single conveyorbelt for transporting containers from the x-ray line scanner subsystem32 to the CT scanner subsystem 34, the orientation and predictability ofpositioning of the containers are insured.

As will also be evident from the description that follows, many featuresof the inspection apparatus 8 provide for high speed inspection ofcontainers. The features providing for high speed inspection ofcontainers in combination generally make provision for inspection of atleast 600 containers per hour.

Radiation Locking

The concept of radiation locking is now described by way of an exampleillustrated in FIG. 3 a to FIG. 3 j.

In the description that follows, the curtain of the first shieldingarrangement 24 is referred to as “the first curtain 56A”, the curtain ofthe second shielding arrangement 26 is referred to as “the secondcurtain 56B” the curtain of the third shielding arrangement 28 isreferred to as “the third curtain 56C”, and the curtain of the fourthshielding arrangement 30 is referred to as “the fourth curtain 56D”.(Compare FIG. 2 with FIG. 3 a).

In the following discussion of FIG. 3 a to FIG. 3 j it can also beinferred that the confines of the inspection tunnel section 14 arecontinuously radiated, unless specifically stated otherwise.

First, as illustrated in FIG. 3 a, a number of closed containers 60, 62are lined up, utilizing conventional airport conveyor belts, in front ofthe first curtain 56A. The first curtain 56A is raised. The secondcurtain 56B remains in a down position so that radiation from theinspection tunnel section 14 is prevented from reaching the loadingtunnel section 12.

Next, as illustrated in FIG. 3 b, a first of the containers 60 is movedthrough the first end of the loading tunnel section 12 into the loadingtunnel section 12. The second curtain 56B remains in a down position.

Next, as illustrated in FIG. 3 c, the first curtain 56A is lowered, thus“locking” the first container 60 between the first curtain 56A and thesecond curtain 56B and hence the concept of “radiation locking”.Radiation locking merely serves to ensure that the first curtain 56A isdown before the second curtain 56B is raised and generally lasts onlyfor a fraction of a second.

Next, as illustrated in FIG. 3 d, the second curtain 56B is raised.Although radiation from the inspection tunnel section 14 may enter theloading tunnel section 12, the radiation is prevented by the firstcurtain 56A from leaving the loading tunnel section 12.

It can already be seen from the discussions of FIG. 3 a to FIG. 3 d thatat least one of the first curtain 56A and the second curtain 56B isalways in a down position, at least when the confines of the inspectiontunnel section 14 are radiated. Radiation is therefore prevented fromleaving the inspection apparatus from a container entry side. Thecontroller (see reference numeral 36 in FIG. 2) may be programmed sothat the line scanner 32 and the CT scanner subsystem 34 are switchedoff when, for whatever reason, both the first curtain 56A and the secondcurtain 56B are at least partially open (or when both the first curtain56A and the second curtain 56B are not entirely closed). Sensors may forexample be provided which detect the positioning of the curtains 56A and56B and which forward the detected information to the controller.

Next, as illustrated in FIG. 3 e, the first container 60 is moved(utilizing the first and second conveyor apparatus 18 and 20—see FIG. 2)from the loading tunnel section 12 into the inspection tunnel section14.

Once the first container 60 is located entirely within the inspectiontunnel section 14, the second curtain 56B is again lowered, asillustrated in FIG. 3 f.

Next, as illustrated in FIG. 3 g, the third curtain 56C is raised andthe first container 60 is moved (utilizing the second and third conveyorapparatus 20 and 22—see FIG. 2) from the inspection tunnel section 14into the unloading tunnel section 16. The fourth curtain 56D remains ina down position so as to prevent radiation, which may enter theunloading tunnel section 16 from the inspection tunnel section 14, fromleaving the inspection apparatus through the second end of the unloadingtunnel section 16.

In the meantime, a second of the containers 62 may be moved into theloading tunnel section 12 in a manner as hereinbefore described withreference to FIG. 3 a to FIG. 3 d. Further movement of the secondcontainer 62 is similar to the movement of the first container 60 ashereinbefore and hereinafter described and should further be evidentfrom the drawings.

Once the first container 60 is located entirely within the unloadingtunnel section 16, the third curtain 56C is again lowered, asillustrated in FIG. 3 h. The first container 60 is thus locked betweenthe third curtain 56C and the fourth curtain 56D, again illustrating theconcept of radiation locking, this time after exit of the firstcontainer 60 from the inspection tunnel section 14. Again, radiationlocking of the first container 60 within the unloading tunnel section 16may last only for a fraction of a second.

As with the first and second curtains 56A and 56B, at least one of thethird curtain 56C and the fourth curtain 56D is always in a downposition, at least when the confines of the inspection tunnel section 14are radiated. Radiation is therefore also prevented from leaving theinspection apparatus from a container exit side. The controller (seereference numeral 36 in FIG. 2) may be programmed so that the linescanner 32 and the CT scanner subsystem 34 are switched off when boththe third curtain 56C and the fourth curtain 56D are at least partiallyopen. Sensors may for example be provided which detect the positioningof the curtains 56C and 56D and which forward the detected informationto the controller.

Next, as illustrated in FIG. 3 i, the fourth curtain 56D is raised andthe first container 60 is moved out of the unloading tunnel section 16through the second end of the unloading tunnel section 16. The thirdcurtain 56C remains in a down position, thus preventing radiation withinthe inspection tunnel section 14 from reaching the unloading tunnelsection 16.

For a complete discussion, FIG. 3 j illustrates the inspection apparatusafter the fourth curtain 56D is lowered. The second container 62 may atthis stage be located within the inspection tunnel section 14. FIG. 3 jis thus similar to FIG. 3 f. The above described steps may then berepeated for a third and following containers.

It should be evident from the aforegoing description of FIG. 3 a to FIG.3 j that one advantage of the inspection apparatus is that the confinesof the inspection tunnel section 14 can be continuously radiated, i.e.without having to turn off a radiation source accompanied by delay ininspection of containers.

Continuous Scanning

Referring briefly to FIG. 3 e to FIG. 3 g, the container 60 is scannedwhile moving into (FIG. 3 e), while located within (FIG. 3 f) and whilemoving out of (FIG. 3 g) the inspection tunnel section 14. The manner inwhich the container 60 is scanned and certain related features are nowdescribed with reference to FIG. 4 a to FIG. 4 c which correspond toFIG. 3 e to FIG. 3 g, respectively.

In the following description of FIG. 3 e to FIG. 3 g, detailed aspectsrelating to software used in the inspection apparatus, are not describedin detail since the patents of Peschmann, referenced previously, teachesthe general principles and techniques whereby objects of interest, suchas explosives hidden in a closed container, are nonintrusively detectedutilizing certain existing x-ray technique-based nonintrusive inspectionapparatus. The Peschmann patents teach many details of the general andspecific implementation of the present invention wherein the x-ray linescanner may be used to form a convention x-ray projection image, and inwhich software programs residing in the memory of a computer may be usedto analyze the x-ray line scanner images, and to identify locationswithin a container being scanned that may deserve more detailed x-raytechnique-based nonintrusive inspection. Peschmann teaches further thatupon identifying such locations in the container, the container may bepositioned with respect to the imaging plane of a CT scanner subsystem,such that a sequence of cross-sectional images of the container may beacquired at the locations so specified. Peschman further teaches thatadditional software programs that may reside in the memory of a computermay be used to analyze the cross-sectional images formed by the CTscanner subsystem, and that additional software programs that may residein the memory of a computer may analyze all of the data available fromboth the x-ray line scanner subsystem and the CT scanner subsystem torender decision as to the likely presence of an object of interest suchas an explosive hidden in the container.

As previously mentioned, the x-ray line scanner subsystem and the CTscanner subsystem (reference numerals 32 and 34 in FIG. 2) are locatedrelatively close to one another. In addition to such a set of generaland specific details of implementation provided by the Peschman patents,the present invention now provides particular scanning methods thatenable the inspection apparatus 8 to be designed more compactly bypermitting imaging planes of the x-ray line scanner subsystem and the CTscanner subsystem to be located closer to one another than would beotherwise possible, while still being capable of achieving a high rateof inspection of containers. What should be understood, however, is thatthe controller (reference numeral 36 in FIG. 2) is programmed to carryout the steps illustrated in FIG. 4 a(i) to FIG. 4 c(ii).

Referring to FIG. 4 a(i), the container 60 is illustrated as it passesfrom the loading tunnel section 12 into the inspection tunnel section14. An imaging plane of the x-ray line scanner subsystem is representedby the line 32 and an imaging plane of the CT scanner subsystem isrepresented by the line 34. The imaging plane 32 of the x-ray linescanner subsystem may be spaced from the second curtain 56B by adistance which is less than the length of the container 60 so that thecontainer 60 starts moving to the imaging plane 32 of the x-ray linescanner subsystem before being entirely located within the inspectiontunnel section 14.

FIG. 4 a(ii) is a view of the container 60, illustrating the container60 after a first front portion 70 has been moved past the imaging plane32 of the x-ray line scanning subsystem. Inspection software analyzingthe image formed by the x-ray line scanning subsystem represents thefirst front portion 70 of the container 60, and may at this stage detecta location 72A within the first front portion 70 which may contain anobject of interest 72B. Alternatively, the inspection software maydetermine, based on other rules, that the specific location 72A withinthe first front portion 70 of the container 60 requires furthermeasurements by the CT scanner subsystem.

Acquisition of the x-ray line scanner image continues whenever thecontainer progresses past the imaging plane 32 of the x-ray line scannersubsystem. This image acquisition does not necessarily require thecontainer to move continuously, nor does it necessarily require thecontainer to move at a constant speed or in a single direction.

Once the location 72A has been identified, the speed at which thecontainer 60 moves may then be progressively reduced and the container60 may be brought to a standstill, as illustrated in FIG. 4 b(i) andFIG. 4 b(ii), with the location of interest 72A located in the imagingplane 34 of the CT scanner subsystem. Movement of the container 60 andacquisition of the x-ray line scanner image is thus position dependentas opposed to, for example, time dependent. Once the container 60 hasstopped, the CT scanner subsystem 34 may scan the location of interest72A.

In the time between identifying the location of interest 72A and thetime at which the container is stopped with the location of interest 72Awithin the imaging plane 34 of the CT scanner subsystem, the x-ray linescanner subsystem may scan a second front portion 74 for of thecontainer 60. A second object of interest 76 may be detected by thex-ray line scanner subsystem 32. Note that the imaging plane 32 of thex-ray line scanner subsystem and imaging plane 34 of the CT scannersubsystem may be spaced from one another by a distance which is lessthan the overall length of the container 60 so that the container 60passes through the imaging plane 34 of the CT scanner subsystem before arear portion 78 of the container 60 passes through the x-ray linescanning plane 32.

The container 60 may then be advanced until the second object ofinterest 76 is located in the imaging plane 34 of the CT scannersubsystem, as illustrated in FIG. 4 c(i) and FIG. 4 c(ii). The imagingplane 34 of the CT scanner subsystem may be spaced from the thirdcurtain 56C by a distance which is less than the overall length of thecontainer 60 so that the container 60 is already partially locatedwithin the unloading tunnel section 16. In the meantime, the x-ray linescanner subsystem 32 may scan the rear portion 78 of the container 60.

Note that the container 60 may therefore be moved through the inspectiontunnel section 14 without altering the direction of movement of thecontainer 60 relative to the x-ray line scanner subsystem 32 and the CTscanner subsystem 34.

Because the first curtain 56B, the imaging plane 32 of the x-ray linescanner subsystem, the imaging plane 34 of the CT scanner subsystem, andthe third curtain 56C are spaced from one another by relatively smalldistances, the overall length of the inspection tunnel section 14 isrelatively short. In one example the imaging plane 32 of the x-rayscanner subsystem is spaced from the first curtain 56B by a distance ofabout 34 centimeters, the imaging plane 34 of the CT scanner subsystemis spaced from the imaging plane 32 of the x-ray line scanner subsystemby a distance of about 87 centimeters, the third curtain 56C is spacedfrom imaging plane 34 of the CT scanner subsystem by a distance of about65 centimeters, and the overall length of the inspection tunnel section14 is therefore about 186 centimeters.

Structural Integrity

FIG. 5 is a perspective view illustrating only the support frame 10 andthe CT scanner subsystem 34. The base frame 38 is of monocoque design.Monocoque designs are frequently used, for example, in the design of thehulls of ships and in the design of the bodies of aircraft. In thepresent example, the base frame 38 generally has the shape of the hullof a ship in that the base frame 38 generally has a channel shape. Othercomponents also form part of the base frame 38 which are similar to abulkhead of a ship.

More specifically, the base frame 38 includes a first monocoque section82, a second monocoque section 84, and a third monocoque section 86. Itshould be understood that the first monocoque section 82 is located inthe region of the loading tunnel section, the second monocoque section84 is located in the region of the inspection tunnel section, and thethird monocoque section 86 is located in the region of the unloadingtunnel section. (See reference numerals 12, 14 and 16 in FIG. 2).

The second monocoque section 84 has a base plate 88, first and secondside walls 90 and 91 respectively, and first and second end walls 92 and93 respectively. The side walls 90 and 91 are secured to the base plate88 and extend upwardly from the base plate 88 and away from one anotherso that the base plate 88 and the first and second side walls 90 and 91jointly define a channel shape which is wider at the top than at thebottom, similar to the hull of a ship when viewed in cross section. Theend walls 92 and 93 are secured at spaced locations within the channelshape defined by the base plate 88 and the side walls 90 and 91, withedges of the end walls 92 and 93 secured to the base plate 88 and theside walls 90 and 91. Each end wall 93 or 94 is similar to a bulkhead ofa ship. The channel shape of the second monocoque section 84 isextremely resistant to bending and the channel shape together with theend walls 93 and 94 also provide torsional resistance to the secondmonocoque section 84.

Further components may be provided which give added support to the baseframe 38. For example, a horizontal deck 95 may be secured to upperedges of the side walls 90 and 91 and the end wall 93, between the endwall 93 and the CT scanner subsystem 34. An additional verticalcomponent 96 may be located on a side of the deck opposing the end wall93 and have an upper edge secured to the deck, side edges secured to theside walls 90 and 91, and a bottom edge secured to the base plate 88.The deck and the additional vertical component are preferably located inthe region of the arch 40 to provide additional rigidity to the baseframe 38 in that region.

The first and third monocoque section 82 and 86 are similar to oneanother in design. Only the first monocoque section 82 is furtherdescribed. It should however be understood that the description of thefirst monocoque section 82 that follows may also hold true for the thirdmonocoque section 86.

The first monocoque section 82 has a base plate 97, first and secondside walls 98 and 100, and an end wall 102. The side walls 98 and 100are secured to the base plate 97 and extend upwardly from the base plate97 and away from one another so that the base plate 97 and the first andsecond side walls 98 and 100 jointly define a channel shape which iswider at the top and at the bottom. The base plate 97 and the side walls98 and 100 are positioned against the side walls 90 and 91 of the secondmonocoque section 84 and secured thereto. The end wall 102 is securedwithin the channel shape defined by the base plate 97 and the side walls98 and 100 and on a side thereof opposing the end wall 93 of the secondmonocoque section 84. The channel shape of the first monocoque section82 provides the first monocoque section 82 with resistance to bendingand the end walls 93 and 102, together with the channel shape, providetorsional resistance to the first monocoque section 82.

The arch 40 has opposing ends 104 and 106 which are secured to the sidewalls 90 and 91, respectively, of the second monocoque section 84. Abearing (not shown) is located within the arch 40 and the CT scannersubsystem 34 is mounted to a rotational portion of the bearing.

In use, the CT scanner subsystem 34 may rotate at a rate of about 120revolutions per minute. Furthermore, it may be required that the CTscanner subsystem 34 be relatively large. One reason for the sizerequirement of the CT scanner subsystem 34 is so that larger containersmay pass through the CT scanner subsystem 34. The CT scanner subsystem34 may, for example define an opening 110 which is about 113 centimetersin diameter.

Another reason for the size requirement of the CT scanner subsystem 34deals with the compatibility of the inspection apparatus with conveyorbelts found within airports. Airport conveyor belts are typically aboutone meter wide. If the conveyor belts used within the inspectionapparatus are less than one meter wide, additional channeling devicesmay have to be provided to reorient and channel containers from theairport conveyor belts to the conveyor belt of the loading tunnelsection. (See reference numerals 50 and 12 in FIG. 2). For example,containers may be oriented on the airport conveyor belts so as to beoriented such that their longest the dimension lies transverse to thedirection of motion of the conveyor belts. With smaller apertureapparatus, channeling devices may then have to be located between theairport conveyor belts and the inspection apparatus to reorient thecontainers so that their longest dimensions line up in a direction whichis more or less parallel to the direction of motion of the conveyorbelts so that the containers fit into the inspection apparatus and ontothe conveyor belts used in the inspection apparatus. Such channelingdevices may add to the overall length of the inspection apparatus andare preferably avoided. The conveyor belts used within the inspectionapparatus 8 are therefore preferably about one meter wide, which meansthat a one-meter wide conveyor belt should be able to pass through theCT scanner subsystem 34.

However, the relatively large diameter of the CT scanner, together withits high rotational rate, may cause very strong forces to be applied tothe base frame 38. The forces may occur inadvertently due to anunbalanced operating condition arising from any cause. Furthermore, therelatively large diameter of the CT scanner subsystem together with arequirement to accelerate quickly to a high rate of revolution, ordecelerate quickly, may cause very strong torsional forces on the baseframe 38 when rotation of the CT scanner subsystem 34 is started orstopped. It should be evident from the aforegoing description that thebase frame 38 is designed to deal with the high forces which may tend tobend or induce vibration in the base frame 38 when the CT scannersubsystem 34 is in an unbalanced condition, for example, and resist therelatively high torsional forces which act on the base frame 38 whenrotation of the CT scanner subsystem 34 is started or stopped.

It should be evident from the aforegoing description that the design ofthe base frame 38 is related to the width of the conveyor belts that areused within the inspection apparatus and that the conveyor belts may besufficiently wide so that reorienting of containers may be avoided. Thecontainers may thus enter the inspection apparatus while being orientedwith their longest dimensions transverse to the direction of motion ofthe conveyor belts. Because the containers may be oriented in such amanner, a container may therefore be oriented so that the width of thecontainer may be located in a direction approximately parallel to thedirection of motion of the conveyor belts, thus potentially permittingcontainer inspection to be completed with a smaller number of CTscanning slices than would be required to complete an equally effectiveinspection were the container to be oriented differently.

Radiation Containment

FIG. 6 illustrates a portion of the arch 40, the inspection tunnelsection 14, the x-ray line scanner subsystem 32, and the CT scannersubsystem 34. The inspection tunnel section 14 includes a first tunnelportion 120, a second tunnel portion 122, and a third tunnel portion 124which are all nonrotatably mounted to the base frame. (See referencenumeral 38 in FIG. 2).

The first tunnel portion 120 is located on a side of the x-ray linescanner subsystem 32 opposing the CT scanner subsystem 34 and has afirst end 126 which is also the first end 42 of the inspection tunnelsection 14, and a second end 128, opposing the first end 126, againstthe x-ray line scanner subsystem 32.

The second tunnel portion 122 is located between the x-ray line scannersubsystem 32 and the CT scanner subsystem 34 and has a first end 130against the x-ray line scanner subsystem 32, and a second end 132,opposing the first end 130, at the CT scanner subsystem 34.

The third tunnel portion 124 is located on a side of the CT scannersubsystem 34 opposing the x-ray line scanner subsystem 32 and has afirst end 134 at the CT scanner subsystem 34 and a second end 136,opposing the first end 134, which is also the second end 44 of theinspection tunnel section 14.

The x-ray line scanner subsystem 32 is nonrotatably mounted to the arch40 and includes a partial gantry enclosure 138 and a radiation tube 140.Other features of the x-ray line scanner subsystem 32 are similar tothose of the CT scanner subsystem 34 and the CT scanner subsystem 34 isdescribed in more detail hereinbelow.

The arch 40 is located around the second tunnel portion 122 and definesa bearing housing 142 around the second tunnel portion 122. The bearinghousing 142 is open towards the CT scanner subsystem 34. A bearing 144is located within the bearing housing 142. The CT scanner subsystem 34includes a gantry enclosure 148, an x-ray tube 150 which is secured tothe gantry enclosure 148, and a ring 152 which is secured to the gantryenclosure 148. The ring 152 extends into the bearing housing 142 and islocated on a rotating portion of the bearing 144, thus mounting the CTscanner subsystem 34 rotatably to the arch 40. The CT scanner subsystem34 rotates around the inspection tunnel section 14.

FIG. 7 illustrates the gantry enclosure 148 and the ring 152 of the CTscanner subsystem 34 in more detail.

The gantry enclosure 148 includes first and second spaced gantry plates,154 and 156 respectively, first, second, and third spacers 158, 160, and162 respectively, a collimator face 164, and a hollow, substantiallyfrustum pyramidal collimator component 165.

The first gantry plate 154 has a gantry aperture 166 formed therein andthe second gantry plate 156 also has a gantry aperture 168 formedtherein. The ring 152 is mounted to the first gantry plate 154 aroundthe gantry aperture 166 in the first gantry plate 154.

The collimator face 164 is curved and a hole 170 is formed in thecollimator face 164. The collimator component 165 has a base 172 whichis slightly larger than the hole 170 in the collimator face 164. Thecollimator component 165 also has an apex 174 which is smaller than thebase 172 and which is formed so as to fit snugly against the x-ray tube.(See reference numeral 150 in FIG. 6). When the base 172 of thecollimator component 165 is positioned over the hole 170 and thecollimator component 165 is mounted to the collimator face 164, the hole170 may only be accessed through the apex 174 of the collimatorcomponent 165.

The first and second gantry plates 154 and 156 are secured to thespacers 158, 160, and 162, with the spacers being located between thegantry plates and around the gantry apertures 166 and 168. The first andsecond spacers 158 and 160 may be made of a material such as aluminum.The third spacer 162 has a curved shape and may also be made of amaterial such as aluminum.

The collimator face 164 may also be made of a material such as aluminumand is shorter than the third spacer 162.

The spacers 158,160, and 162 and the collimator face 164 are positionedin a trapezium-like shape with the third spacer 162 and the collimatorface 164 respectively forming a long side and a short side of thetrapezium and the first and second spacers 158 and 160 connecting edgesof the third spacer 162 and the collimator face 164 so that the firstand second spacers 158 and 160 are spaced closer to one another at thecollimator face 164 and further from one another at the third spacer162.

The gantry enclosure 148 is so partially defined by the first and secondgantry plates 154 and 156, the spacers 158, 160, and 162, and thecollimator face 164. The only areas of the gantry enclosure 148 whichare open are due to the gantry apertures 166 and 168 in the first andsecond gantry plates 154 and 156 respectively, and due to the hole 170in the collimator face 164.

The gantry enclosure 148 includes lead lining which prevents radiationfrom escaping from the gantry enclosure 148. Lead tiles 176 are mountedto the third spacer 162 within the gantry enclosure 148. Lead plates178, 180 are also secured to the first spacer 158 and the second spacer160, respectively, within the gantry enclosure 148, and a lead plate 182is secured to the collimator face externally of the gantry enclosure148. A lead liner 184 is also secured to the first gantry plate 154 on aside thereof facing into the gantry enclosure 148, and another leadliner 186 is secured to the second gantry plate 156 on a side thereoffacing into the gantry enclosure 148. The lead liners 184 and 186conform to the internal dimensions of the gantry enclosure 148. Inaddition, the collimator component 165 is made of the lead. It can thusbe seen that the entire gantry enclosure 148 is lead lined and thusresistant to transmission of x-ray radiation. The only areas throughwhich x-ray radiation may pass into or out of the gantry enclosure 148are the apex 174 of the collimator component 165 and the gantryapertures 166 and 168 in the first and second gantry plates 154 and 156,respectively.

Referring again to FIG. 6, the x-ray tube 150 fits snugly on the apex174 of the collimator component 165. A lead lining 188 covers all innersurfaces of the x-ray tube 150, except an area of the x-ray tube 150directly over the apex 174 of the collimator component 165. The entirearea including the x-ray tube 150 and the collimator component 174 isthus enclosed by lead. It should now the evident that, when the x-raytube 150 is activated, x-rays are transmitted from the x-ray tube 150through the collimator component 165 into the confines of the gantryenclosure 148. X-ray radiation may only escape through the gantryapertures 166 and 168 in the first and second gantry plates 154 and 156respectively.

Detector arrays 190 are located within the gantry enclosure 148 on aside of the gantry enclosure 148 opposing the x-ray tube 150. Thedetector arrays 190 may for example be mounted to the lead tiles 176.Conductors 192 are connected to the detector arrays 190 and extendthrough the lead tiles 176 and the third spacer 162 so as to provide anelectrical connection between the detector arrays 190 and externally ofthe gantry enclosure 148.

The x-ray line scanner subsystem 32 may have a similar construction tothe CT scanner subsystem 34 and is lead lined in a manner similar to theCT scanner subsystem 34.

Lead linings 196, 198 and 200 are also formed on the internal dimensionsof the first, second and third tunnel portions 120, 122 and 124,respectively. Lead linings 196 and 198 of the first and second tunnelportions 120 and 122 are sufficiently dose and overlapping the leadlinings of the x-ray line scanner subsystem 32 so that interfacesbetween the x-ray line scanner subsystem 32 and the first and secondtunnel portions 120 and 122 are, in a radiation sense, substantiallysealed.

The second end 132 of the (stationary) second tunnel portion 122 extendsinto the gantry aperture 166 in the first gantry plate 154 of the(rotatable) CT scanner subsystem 34. The lead lining 198 on the secondtunnel portion 122 is located relatively dose and overlapping the leadliner 184 on the first gantry plate 154 and is separated therefrom onlyby a gap which is necessary to allow for rotation of the CT scannersubsystem 34 relative to the second tunnel portion 122. And interfacebetween the second tunnel portion 122 and the CT scanner subsystem 34 isthus, in a radiation sense, substantially sealed.

Similarly, the first end 134 of the third tunnel portion 124 extendsinto the gantry aperture 168 of the second gantry plate 156, and thelead lining 200 is located relatively dose to the lead liner 186 so thatan interface between the third tunnel portion 124 and the second gantryplate 156 is, in a radiation sense, substantially sealed.

Referring again to FIG. 2, the internal dimensions of the loading andunloading tunnel sections 12 and 16 are also lead lined. Each curtain 56is made of a number of layers which are located over one another,including a number of layers containing significant amounts of lead.

It should be evident that the entire inspection apparatus 8 is selfshielded against in the sense that it effectively attenuates leaking ofradiation therefrom and that no extraneous radiation resistant shieldingmembers have to be provided for purposes of radiation containment.Because no extraneous radiation shielding members have to be provided,much less lead lining is required—see for example how the x-ray tube 150is lead lined with the minimal amount of lead.

The lead on the CT scanner subsystem 34 does make it somewhat heavier,with corresponding consequences as far as stresses and strains on thebase frame are concerned. (See reference numerals 38 in FIG. 5). Thebase frame is, as described with reference to FIG. 5, however designedto deal with relatively large forces.

Although self shielding has been specifically described with referenceto an x-ray technique-based nonintrusive inspection apparatus forinspection of containers, the principles of self shielding may also findapplication in related technologies such as CT scanning of people andother patients. A self shielded CT scanner may be located within a roomand be used for inspecting and diagnosing of a patient. Since the CTscanner is self shielded, the patient may be inspected, utilizing the CTscanner, while people are located around the CT scanner within the sameroom. Furthermore, such self-shielded apparatus would obviate the needand cost of providing special rooms with walls, floors, and ceilingswhich are capable of providing such radiation shielding

Driving Arrangement

FIG. 8 illustrates in end view the CT scanner subsystem 34 and a drivingarrangement 210 forming part of the x-ray technique-based nonintrusiveinspection apparatus and which is used for rotating the CT scannersubsystem 34.

It should be evident from the aforegoing description that the CT scannersubsystem 34 is rotatably mounted to the arch of the support frame. (Seefor example reference numerals 10 and 40 in FIG. 2 and FIG. 5). The CTscanner subsystem 34 has a circular outer surface 212 which may, forexample, be on a ring which may be secured to the gantry enclosure. (Seereference numeral 148 in FIG. 6).

The driving arrangement 210 includes first, second and third pulleys214, 216 and 218, respectively, an electric motor 220, and a flexiblemember 222, such as a flexible belt or a chain, forming a closed loop.The pulleys 214, 216 and 218 are located at various locations around theC. T. scanner subsystem 34. The first and second pulleys 214 and 216 arerotatably mounted to the support frame. (See reference numeral 10 inFIG. 2). The electric motor 220 is also mounted to the support frame andthe third pulley 218 is directly coupled and mounted to a shaft of theelectric motor 220 so as to be rotated by the electric motor 220 whenthe electric motor 220 is operated.

The flexible member 222 encircles and runs over the first, second andthird pulleys 214, 216 and 218, respectively. When stationary, or at anygiven moment while moving over the pulleys 214, 216, and 218, theflexible member 222 has a first section 224 running from the firstpulley 214 to the second pulley 216 in a first direction 226 around andover the circular outer surface 212. The flexible member 222 also has asecond section 228 returning from the second pulley 216 over the thirdpulley 218 back to the first pulley 214 in a second direction 230, whichis opposite to the first direction 226, around the circular outersurface 212.

In use, when the third pulley 218 is rotated by the electric motor 220,the flexible member 222 progresses over the pulleys 214, 216 and 218,for example in an anti-clockwise direction. Because of progression ofthe flexible member 222, the CT scanner subsystem 34 is rotated in aclockwise direction

It can thus the seen that a complete revolution of the flexible member222 does not entirely encircle the CT scanner subsystem 34. Because ofthe positioning of the flexible member 222, it may be engaged with thecircular outer surface 212 without having to be positioned so that itsurrounds the CT scanner subsystem 34, the inspection tunnel section, orthe inspection conveyor apparatus. The flexible member 222 may thus beinstalled without obstruction from the CT scanner subsystem 34 itself orobstruction from the inspection tunnel section of the inspectionconveyor apparatus which are mounted to the base portion in the vicinityof the CT scanner subsystem 34. (See reference numerals 14, 20 and 38 inFIG. 1). Maintenance due to failure of the flexible member 222 is thusgreatly simplified.

In other embodiments more pulleys may be used serving various purposessuch as tensioning of the flexible member 222, or the flexible member222 may be driven by a separate device.

Shielding Arrangements

FIG. 9 illustrates one of the shielding arrangements 24, 26, 28 or 30 ofFIG. 2 in more detail. The shielding arrangement 24, 26, 28 or 30 formspart of a larger shielding apparatus which includes support structures240 which are mounted to the base frame and which form part of thesupport frame of the x-ray technique-based nonintrusive inspectionapparatus of the invention. (See reference numerals 8,10 and 38 in FIG.2). Each shielding arrangement 24, 26, 28 or 30 includes, in addition tothe curtain roller 54 and the radiation resistant curtain 56, also anelectric motor 242, a tensioning roller 244, a flexible sheet 246, and atorsion spring 248.

The curtain roller 54 is rotatably mounted between the supportstructures 240, and the curtain 56, as previously mentioned, is securedto the curtain roller 54 so as to be rolled onto or from the curtainroller 54 upon rotation of the curtain roller 54.

The electric motor 242 is also secured to one of the support structures240. A driving belt 250 couples the electric motor 242 to the curtainroller 54 so that the curtain roller 54 is rotated upon operation of theelectric motor 242. The rotational positioning of the curtain roller 54,and therefore also the height of the curtain 56, is also determined bythe electric motor 242.

The sheet 246 has one portion attached to the curtain roller 54 and asecond portion attached to the tensioning roller 244. The sheet 246 isrolled onto the tensioning roller 244.

The tensioning roller 244 is also rotatably mounted between the supportstructures 240. The torsion spring 248 is located between one of thesupport structures 240 and that tensioning roller 244. The torsionspring 248 is under torsion, i.e. the torsion spring 248 is torsionallybiased, thus tending to rotate the tensioning roller 244. The tensioningroller 244 is, however, prevented from rotating because the tensioningroller 244 is connected by the sheet 246 to the curtain roller 54 andthe rotational position of the curtain roller 54 is determined by theelectric motor 242. It should thus be evident that the sheet 246 isunder tension between the curtain roller 54 and the tensioning roller244 because of the tendency of the tensioning roller 244 to rotate andthe predetermined rotational positioning of the curtain roller 54.

FIG. 10 illustrates the arrangement of FIG. 9 in end view. The curtain56 hangs from one side of the curtain roller 54. The tensioning roller244 is located on the same side of the curtain roller 54 as the side ofthe curtain roller 54 from which the curtain 56 hangs, with the curtain56 being located between the curtain roller 54 and the tensioning roller244.

The sheet 246 passes from under the tensioning roller 244 over and ontothe curtain roller 54. The sheet 246 therefore extends clockwise aroundthe tensioning roller 244 and anti-clockwise around a portion of thecurtain roller 54.

The tensioning roller 244 has a tendency to rotate in an anti-clockwisedirection 251. Because of the tendency of the tensioning roller 244 torotate in an anti-clockwise direction, and the connection between thetensioning roller 244 and the curtain roller 54, the curtain roller hasa tendency to rotate in a clockwise direction. Rotation of the curtainroller 54 in an anti-clockwise direction results in rolling of thecurtain 56 onto the curtain roller 54 and rotation of the curtain roller54 in a clockwise direction results in rolling of the curtain 56 fromthe curtain roller 54. The tensioning roller 244 thus tends to roll thecurtain 56 from the curtain roller 54.

The tensioning roller 244 and the sheet 246 ensure that the curtain 56is rolled tightly and in a controlled manner onto the curtain roller 54.The tensioning roller 244 and the sheet 246 also ensure that the curtain56 remains tightly on the curtain roller 54 when rotation of the curtainroller 54 in an anti-clockwise direction is decelerated. The tensioningroller 244 and the sheet 246 also ensure that the curtain 56 remainstightly on the curtain roller 54 when the curtain roller 54 is rotatedin a clockwise direction.

For example, FIG. 11 illustrates the arrangement of FIG. 10 when thecurtain 56 is rolled onto the curtain roller 54 by rotation of thecurtain roller 54 in an anti-clockwise direction 252. The sheet 246 isrolled together with the curtain 56 onto the curtain roller 54 with thesheet 246 being located on an outer surface of the curtain 56. Due tothe tension present in the sheet 246, the sheet 246 creates a force 254on the curtain 56 which is radially inward towards the curtain roller54. Because of the force 254, the curtain 56 is maintained in closecontact with the curtain roller 54 and preceding layers of the curtain56 when the curtain 56 is rolled onto the curtain roller 54.

When the curtain roller 54 is rotated in an anti-clockwise direction,the curtain 56 has momentum. When the curtain roller 54 is brought to ahalt, after being rotated in an anti-clockwise direction, the momentumof the curtain 56 will tend to lift the curtain 56 from the curtainroller 54 or preceding layers of the curtain 56 on the curtain roller54. The tendency of the curtain 56 to lift is, however, counteracted bythe force 254.

When the curtain roller 54 is accelerated in a clockwise direction, lackof momentum of the curtain 56 will attend tend to cause the curtain 56to lift, which tendency is again counteracted by the force 254.

By correctly positioning the tensioning roller 244, the trajectory ofthe curtain 56 when it rolls off the curtain roller 54 can also becontrolled. The trajectory of the curtain 56 is preferably substantiallyvertically downwardly. Vertical downward movement of the curtain 56 ispreferred because waves within the curtain 56 or whiplash-likeoscillations of the curtain 56 can so be avoided and the curtain 56 canthus the brought to standstill much quicker.

Referring again to FIG. 10, it should also be noted that the curtainroller 54 has an outer surface which has a shape which is generally inthe form of a spiral having a step 260. An end of the curtain 56 issecured to an inner portion 262 of the spiral with a edge of the curtain56 adjacent the step 260. A surface 264 of the curtain 56 opposing theinner portion 262 is substantially in line with an outer portion 266 ofthe spiral.

When the curtain 56 is rolled onto the curtain roller 54, as illustratedin FIG. 10, up to the point where the curtain 56 starts rolling ontoitself (the sheet 246 being located between layers of the curtain 56) asmooth transition is ensured. A smooth transition is important becausewaves within or whiplash-like oscillations of the curtain 56 may beavoided, and the power demanded of the drive motor is made more uniformin time. When the curtain 56 is rolled from the curtain roller 54 asmooth transition is also ensured which, in addition to the positioningof the tensioning roller 244, further prevents waves within orwhiplash-like oscillations of the curtain 56.

It can thus be seen from the aforegoing description that the curtain 56may be lowered and raised quickly and in a controlled manner bothbecause of the tensioning roller 244 and the spiral shape of the curtainroller 54.

Detector Array Collimators

FIG. 12 a(i) to FIG. 12 c(ii) illustrate a method of making a collimatorfor a detector array of the CT scanner. (See reference numeral 34 inFIG. 2).

FIG. 12 a(i) illustrates a die 310 which may be used for injectionmolding of such a body of a collimator. The die 310 includes a cup 312and a shape defining element 314. The shape defining element 314includes a substructure 316 and a plurality of fins 318 which aresecured to the substructure 316. The fins 318 define a plurality ofsepta gaps 320 between them.

Referring to FIG. 12 a(ii), the shape defining element 314 also includesdelimiting portions 322 secured to the substructure 316 on opposingsides of the fins 318. The fins 318 are slightly longer than thedelimiting portions 322.

FIG. 12 b(i) illustrates the die 310 after the shape defining element314 is inserted into the cup 312. The fins 318 extend all the way to abase of the cup 312.

In FIG. 12 b(ii) it can be seen that L-shaped support structure gaps 324are formed between opposing surfaces of the fins 318 and the delimitingportions 322, and between the delimiting portions 322 and the base ofthe cup 312. In another section through FIG. 12 b(i), one will be ableto see that the support structure gaps 324 and the septa gaps 320 are incommunication with one another.

A material is injected into one of the support structure gaps 324 sothat the material fills the support structure gaps 324 and the septagaps 320. The material preferably comprises about 86 percent lead, 3percent tin, and 11 percent antimony. The lead provides the materialwith x-ray radiation shielding capabilities, while the purpose of thealloy between the elements is to provide the material with the strengththat lead, by itself, lacks.

The material is then allowed to set within the die 310 to form a body ofa collimator which is then removed from the die 310 as will be furtherdescribed hereinbelow with reference to FIG. 14. FIG. 12 c(i)illustrates the body 330 of the collimator 332. The body 330 has aplurality of septa 334, formed in the septa gaps 320, which are locatednext to one another.

Referring to FIG. 12 c(ii), it can be seen that support structures 336are formed within the support structure gaps 324 and that the septa 334are secured between and supported by the support structures 336. Thesupport structures 336 include mounting portions 338 which are coplanarwith one another, and walls 340 extending from the mounting portions 338parallel to one another.

FIG. 13 is a perspective view of the collimator 332. Registrationnotches 341 are formed within sides of the mounting portions 338. Theregistration notches 341 allow for positioning and securing of aplurality of collimators such as the collimator 332 simply, reliably,and accurately in a modular fashion.

It can be seen from the aforegoing description that an effective andeasy method is provided for forming the body 330 of the collimator 332.

More importantly, the body 330 has superior strength characteristicsbecause of the materials used for forming the body and because of themanner in which the septa 334 are secured between the support structures336. The collimator 332 may be located on a detector array of the CTscanner subsystem (see reference numeral 34 in FIG. 2) wherein thedetector array rotates at a relatively large radius. The CT scannersubsystem may, in addition, rotate at a relatively high rate ofrevolution. The radius of rotation of the detector array, together withthe relatively high rate of revolution of the CT scanner subsystem maycause large centrifugal forces to act on the collimator 332. Thestrength characteristics of the body 330 of the collimator 332 are thusimportant for dealing with the centrifugal forces.

FIG. 14 illustrates in much exaggerated detail an x-ray tube 150 whichis used in the CT scanner subsystem (see reference numeral 150 in FIG.6), and a view of the septa 334 when the collimator 332 of FIG. 12 andFIG. 13 is installed on a detector array (not shown).

Each septum 334 has first and second opposed surfaces 342 and 344,respectively, and a center line 346 between the surfaces 342 and 344.The center lines 346 converge towards one another in a direction 348 andmeet at the x-ray tube 150. Because of the orientations of the centerlines 346 relative to one another, x-rays 350 which are emitted by thex-ray tube 150 may pass through collimator apertures 352 between thesepta 334 in a manner wherein the x-rays 350 are correctly collimated.

Surfaces 342 and 344 of two of the septa 334 which face one another do,however, not converge in the direction 348. As shown in the drawing, itmay be possible that the opposing surfaces 342 and 344 of two of thesepta 334 located next to one another may diverge from one another inthe direction 348. The reason for the orientations of the opposingsurfaces 342 and 344 relative to one another is so that the fins (seereference numeral 318 in FIG. 12 b(i)), when the septa 334 aremanufactured, may be removed. Each fin will therefore have opposingsurfaces which are substantially parallel to one another or which tapertowards one another in a direction from the substructure (see referencenumeral 316 in FIG. 12 a(i)) towards tips of the fins.

As mentioned, FIG. 14 is in greatly exaggerated detail. The anglesbetween the center lines 346 of the septa 334 are, in practice, muchsmaller than indicated in FIG. 14. Removal of the fins is therefore notsubstantially hampered because of the angles of the center lines 346relative to one another. In practice, for example, sixteen of the septa334 may be provided, a lower tip of a first of the septa may be spacedfrom a lower tip of a sixteenth of the septa by a distance of about 50millimeters, and an upper tip of the first septum may be spaced from anupper tip of the sixteenth septum by a distance of about 49 millimeters.

Container Jam Release

FIG. 15 illustrates one of the conveyor apparatus 18 or 22 and itsinteraction with the base frame 38. (Compare FIG. 15 with FIG. 2).

Rails 410 are located on opposing sides of the base frame 38. A lever412 is pivotally mounted to a portion 414 of the base frame 38. Handles416 are mounted to ends of the lever 412. A pin 418 is secured to thelever 412 intermediate a pivot axis 420 of the lever 412 and one of thehandles 416.

The conveyor apparatus 18 or 22, in addition to the front conveyorroller 46, the rear conveyor roller 48, and the conveyor belt 50(compare with FIG. 2), further includes a conveyor slider plate 424 anda number of bracket assemblies 426. The bracket assemblies 426 aremounted directly to the conveyor slider plate 424 and the front and rearconveyor rollers 46 and 48 are, in turn, rotatably mounted betweenrespective sets of the bracket assemblies 426.

The conveyor apparatus 18 or 22 as shown in FIG. 15 may be preassembledby a subcontractor. The subcontractor may also tension the conveyor belt50 of the conveyor apparatus 18 or 22 before the conveyor apparatus 18or 22 is supplied to another entity which mounts the conveyor apparatus18 or 22 to the base frame 38.

A slot 428 is formed through the conveyor slider plate 424. The slot 428extends in a direction transverse to the direction of motion of theconveyor belt 50, and therefore substantially parallel to the front andrear conveyor rollers 46 and 48.

The arrows 430 indicate mounting of the conveyor apparatus 18 or 22 ontothe base frame 38. The conveyor slider plate 424 nestles between and onthe rails 410 so as to be movable only in a direction 432 in which therails 410 extend. The pin 418 is aligned with the slot 428 so that thepin 418 extends through the slot 428 when the conveyor slider plate 424is located on the rails 410.

An operator may move one of the handles 416 so that the lever 412rotates about the pivot axis 420. Rotation of lever 412 causes rotationof the pin 418 about the pivot axis 420. The pin 418 engages within theslot 428 within the conveyor slider plate 424 so that the conveyorapparatus 18 or 22 is moved backward or forward along the rails 410. Thepin 418 also slides along the slot 428 when the lever 412 is rotated.Movement of the pin 418 along the slot 428 is limited by the length andpositioning of the slot 428 so that movement of the conveyor apparatus18 or 22 along the rails 410 is also limited.

Although only one of the conveyor apparatus 18 or 22 is shown in FIG.15, it should be understood that both of the conveyor apparatus 18 and22, as shown in FIG. 2, have a design similar to that shown in FIG. 15.The conveyor apparatus 20 is rigidly mounted to the base frame 38, sothat only the conveyor apparatus 18 and 22 are able to be moved bymoving its respective lever 412.

In use, the conveyor apparatus 18, 20 and 22 are mounted to the rails410 in such a manner that adjacent front and rear rollers 46 and 48thereof are located fairly close to one another. By so locating theconveyor apparatus 18, 20 and 22 relative to one another, smoothtransition of containers from one conveyor apparatus to another isensured. It may, however, happen from time to time that parts ofcontainers, such as belts on luggage, become jammed between adjacentones of the front and rear conveyor rollers 46 and 48 of two of theconveyor apparatus which are located sequentially one after the other.One of the conveyor apparatus 18 or 22 may then be moved away from theconveyor apparatus 20 by moving the handle 416 thereof, so as to partadjacent ones of the front and rear conveyor rollers 46 and 48 of thetwo conveyor apparatus. The jammed parts of containers can then bereleased from between the adjacent conveyor apparatus.

Ideally, the conveyor apparatus 18 or 22 should not, under normaloperating conditions, be able to float freely on the rails 410. Anadditional mechanism may be provided which may lock the lever 412releasably into a number of predetermined positions. Other mechanismsmay also be provided for controlling movement of the conveyor sliderplate 424 along the rails 410, and for controlling the orientation ofthe conveyor slider plate 424 relative to the rails 410. Such mechanismsare known in the art.

Air Conditioning

FIG. 16 of the accompanying drawings illustrates the inspectionapparatus 8 which further includes paneling around all the componentsheretofore described with the exclusion notably of the controller (seereference numeral 36 in FIG. 2) and the base frame 36. The paneling, inparticular, is located around the tunneling which is formed by theloading tunnel section 12, the inspection tunnel section 14, and theunloading tunnel section 16, and around the x-ray line scanner subsystem32 and the CT scanner subsystem 34.

The paneling includes a plurality of contiguous panels 510 which matchup with one another and which, together with the base frame 38, define ahousing 512 around the other components of the inspection apparatus 8.

One of the panels 510A is located at the first end 42 of the loadingtunnel section 12. The panel 510A has an entry aperture 514 which is inclose proximity to the first end 42 of the loading tunnel section 12.Another one of the panels 510B is located at the second end 44 of theunloading tunnel section 16. The panel 510B has an exit aperture 515which is in close proximity to the second end of the unloading tunnelsection 16.

More of the panels 510C and 510D are sliding doors which are slidablymounted to the base frame 38 to provide access to the x-ray line scannersubsystem 32 and the CT scanner subsystem 34. When the panels 510C and510D are closed, a fairly tight interface 516 is formed between thepanels 510C and 510D.

From the aforegoing can generally be noted that a housing 512 isrelatively airtight.

FIG. 17 is a view of the inspection apparatus 8 which furtherillustrates an air-conditioning apparatus 520 forming part of theinspection apparatus 8. The housing 512 is shown to have an air inletopening 522 and an air outlet opening 524. The gantry enclosure 148 isalso shown together with the ring 152 and the bearing 144 which mountthe gantry enclosure 148 rotatably to the arch 40.

The air-conditioning apparatus 520 includes an air inlet duct 526, anair-conditioning unit 528, an air supply duct 530, a plenum 532, aradiator 534, and an air return duct 536.

The air-conditioning unit 528 is located externally of the housing 512and includes a fan 538.

The plenum 532 is nonrotatably mounted to the support frame of theinspection apparatus (see reference numeral 10 in FIG. 2) and is in theform of a ring which is located around the ring 152. The plenum 532 alocated externally of the gantry enclosure 148 next to the first gantryplate 154 of the gantry enclosure 148. The plenum 532 has a recessedshape which is open towards the gantry enclosure 148. A number of airpassages 542 are formed through the first gantry plate 154. The(non-rotating) plenum 532 is located over the air passages 542 so thatthe confines of the plenum 532 are in communication with the confines ofthe (rotating) gantry enclosure 148.

The radiator 534 is mounted on an outer surface of the gantry enclosure148 and holes (not shown) are formed in the gantry enclosure 148 whichplace the confines of the gantry enclosure 148 in communication with theradiator 534. Note that no fan is mounted within the gantry enclosure148.

The air inlet duct 526 has one end at atmospheric pressure and anotherend connected to, and in communication with, the air-conditioning unit528. The air supply duct 530 extends through the air inlet opening 522and has one end connected to, and in communication with, theair-conditioning unit 528 and an opposing end connected to, and incommunication with, the confines of the plenum 532. The air return duct536 has one end connected to, and in communication with, the air outletopening 524 and an opposing end connected to, and in communication with,the air-conditioning unit 528.

In use, air flows into the air-conditioning unit 528 when the fan 538rotates. The air enters the air-conditioning unit 528 substantially atatmospheric pressure and atmospheric temperature. The air then passesthrough the air-conditioning unit 528. The air-conditioning unit 528lowers the temperature of the air to substantially below atmospherictemperature. The fan 538 also increases the pressure of the air to aboveatmospheric pressure.

The air is then drawn into the housing 512 through the air supply ductat above atmospheric pressure and below atmospheric temperature. The airthen flows through the air supply duct 530 into the plenum 532 fromwhere the air flows through the air passages 542 into the gantryenclosure 148. A window 543 is located between the gantry apertures 166and 168 so that a confined volume is defined by the window 546, thegantry plates 154 and 156, and the spacer 160. A number of plates (notshown) are located at selected angles around a revolution of the gantryenclosure 148 and extend radially outward so that individual confinedvolume pockets are defined around a revolution of the gantry enclosure.The air enters selected ones of these pockets through selected ones ofthe air passages 542, notably a pocket at the radiator 534 and a pocketin which the detectors (190 in FIG. 6) are located.

Air then flows from each pocket through holes (not shown) out of thegantry enclosure 148. The air flows from one pocket through some of theholes in the spacer 160 to the radiator 534. The air then passes throughthe radiator 534. The radiator 534 is used for cooling the x-ray tube(see reference numeral 150 in FIG. 6) and, when operated, is at atemperature substantially above atmospheric temperature. The air is usedto cool the radiator 534. When the air flows through the radiator 534,the temperature of the air increases somewhat, but still remains belowatmospheric temperature. The air also remains above atmosphericpressure.

Referring now to FIG. 16 and FIG. 17 in combination, once the air passesthrough the radiator 534, the air is located within a volume 540 whichis externally of the tunneling provided by the loading inspection andunloading tunnel sections 12, 14 and 16, respectively, externally of thex-ray line scanner subsystem 32, and externally of the gantry enclosure148, but still contained within the housing 512. As mentioned, thehousing 512 is in close proximity to and therefore seals relativelytightly on the loading and unloading tunnel sections 12 and 16, at leastto an extent sufficient to maintain the above atmospheric pressure ofthe air within the housing 512. As also mentioned, the interface 516 isalso relatively airtight. The housing 512, in all other respects, isformed to maintain the above atmospheric pressure within the housing512.

The air then flows from the housing 512 through the air outlet opening524 and the air return duct 536 back to the air-conditioning unit 528.The air-conditioning unit 528 may control the ratios of air flowingrespectively from the air inlet duct 526 and the air return duct 536 sothat the air within the volume 540 remains above atmospheric pressure.

Because the air within the volume 540 remains above atmosphericpressure, and therefore above the pressure of the air externally of thehousing 512, the air may leak slightly from between adjacent panels 510of the housing 512 in a direction from within the housing 512 to an areaaround the housing 512. Because of the direction of leaking of air,ingress of dirt, moisture, and other contaminants into the housing 512may be avoided. The positive pressure within the housing 512 thusprotects the components within the housing 512 from dirt, moisture, andother contaminants.

It should be evident from the aforegoing description that thetemperature of the air in the volume 540 is still below atmospherictemperature, as required for improved, more stable, and more reliableoperation of components such as detector arrays which are used withinthe inspection apparatus 8.

What should also be noted from FIG. 17 is the positioning of the fan538. The fan 538 is located externally of the gantry enclosure 148. Thefan 538 is thus protected from gyroscopic forces which may otherwise acton the fan 538 should the fan 538 be located on the gantry enclosure148. By so locating the fan 538, the gantry enclosure 148 can be rotatedat higher speeds that would otherwise be possible. The gantry enclosure148 can also be made larger without being limited by possiblemalfunctioning of the fan 538.

As previously mentioned, the invention is described by way of exampleonly. In the aforegoing description and example is given of apparatusand a method for inspecting closed containers before being loaded into aloading bay of an airplane. Such use may, for example, be for thedetection of explosives within closed containers. It should however beunderstood that the invention is not to be limited to the inspection ofa closed containers before being loaded into a loading bay of anairplane. Various aspects of the invention may for example findapplication in the detection of contraband and illicit materialsgenerally, applications beyond those linked to aviation, such as railtravel, the inspection of mail or parcels, materials testing andcharacterization, and the inspection of patients, in particular thoseapplications utilizing CT technology.

1. A method of non-intrusively inspecting an object (60), utilizing anx-ray technique-based nonintrusive inspection apparatus, including:scanning a front portion (70, 74) of the object utilizing an x-ray linescanner subsystem (32); scanning a section (72A) within the frontportion utilizing a CT scanner subsystem (34); and scanning a rearportion (78) of the object, utilizing the x-ray line scanner subsystem,after the section in the front portion is scanned with the CT scannersubsystem.
 2. A method according to claim 1 wherein the object isscanned while being moved relative to the x-ray line scanner subsystemand the CT scanner subsystem and the front portion and the rear portionare scanned without altering the direction of movement of the objectrelative to the x-ray line scanner subsystem and the CT scannersubsystem.
 3. A method according to claim 1 wherein the movement of theobject relative to the x-ray line scanner subsystem and the CT scannersubsystem is progressively reduced after the section is scanned by thex-ray line scanner subsystem but before the section is scanned by the CTscanner subsystem.
 4. An x-ray technique-based nonintrusive inspectionapparatus (8) which includes: at least one tunnel section (14) havingfirst and second opposed ends (42, 44); a conveyor system (20) having atleast one belt (50), at least partially located within the tunnelsection, which, upon movement, is capable of transporting an object fromthe first end to the second end of the tunnel section; an x-ray linescanner subsystem (32) which is positioned to scan at a first planewithin the tunnel section; a CT scanner subsystem (34) which ispositioned to scan at a second plane within the tunnel section, whereinthe same belt of the conveyor system conveys the object from first planeto the second plane; and at least one shielding arrangement (26) securedto one end of the tunnel section, having a curtain roller (54) and aradiation resistant curtain (56) secured to the curtain roller.
 5. Anx-ray technique-based nonintrusive inspection apparatus (8) whichincludes: a base frame (38); a support structure (40) having a lower end(104, 106) secured to the base frame and extending upwardly therefrom;an x-ray line scanner subsystem (32) mounted to the support structure; aCT scanner subsystem (34) rotatably mounted to the support structure;and at least one shielding arrangement (26), having a curtain roller(54), and a radiation resistant curtain (56) secured to the curtainroller, wherein the curtain roller is rotatably mounted to the supportstructure.